Aircraft experience electromagnetic effects (EME) from a variety of sources, such as lightning strikes and precipitation static. Metallic aircraft structures are readily conductive and, therefore, are relatively less susceptible to electromagnetic effects. Basic epoxy-based composite aircraft structures, however, do not readily conduct away the significant electrical currents and electromagnetic forces stemming from electromagnetic effects. Therefore, when composites are used on an aircraft, steps are often taken to protect against electromagnetic effects, such as by incorporating conductive materials into the composites.
Fasteners with integral dielectric layers have been developed in an attempt to provide protection against electromagnetic effects. For example, U.S. Pat. Pub. No. 2013/0259604 discloses a fastener having a fastener head and a layer of dielectric material mechanically attached to the fastener head. The layer of dielectric material may include a polymeric material, such as polyether ether ketone.
Polyether ether ketone is commonly used in the aerospace industry due to its dielectric properties, its ability to maintain strength at elevated temperatures, and its chemical resistance. However, the limited toughness of polyether ether ketone has curtailed its application as a dielectric material in connection with electromagnetic effects-protective fasteners.
Accordingly, those skilled in the art continue with research and development efforts in the field of electromagnetic effects protection.